Marksmanship training in the use of automatic weapons, such as machine guns, has been widely accomplished in recent years using lasers instead of bullets for scoring. This is done to solve problems related to both economy and safety. A machine gun capable of firing a thousand rounds of ammunition a minute can consume thousands of dollars in ammunition in a single day's service on a gunnery range, and also can represent a substantial hazard in the hands of inexperienced trainees.
The employment of a laser beam that is aligned with the weapon's sight offers a solution to both of the above problems by providing a means of showing where the gun is aimed during firing, but it does not provide any realism for the shooter in terms of sound (peak pressure in db and timbre), flash and smoke. Therefore a common practice has been to fire blank ammunition in these guns to make the training more realistic. This practice enhances safety by eliminating the actual bullets, but it requires the use of ammunition casings, primers, wadding and powder; as well as continuing the need for loading, handling and cleaning up brass after firing. Misfires of automatic weapons are common, as blanks have only a marginal amount of energy to reliably reload the chamber. Therefore it is still a costly method of providing realism for training.
More recent training systems have included automatic weapons effects signature simulators to provide the sound (db and timbre), flash and smoke for laser firing simulated machine guns. These devices operate by injecting pulses of a combustible gaseous fuel and an oxidizer into a combustion chamber and then igniting the mixture with a spark plug. In this manner the use of real or blank ammunition is replaced with fuel and oxidizer, pulsed under pressure into a combustion chamber through trigger operated solenoid valves.
Previously known prior art weapons effects simulating combustion chambers have had somewhat limited performance, due to the improper design of the injectors and combustion chamber. In order to meet the real weapon requirements of sound pressure level during high firing rates typical of automatic weapons, injection and mixing of fuel and oxidizer must be accomplished in a turbulent fashion, followed by ignition and rapid transition to a combustive detonation wave. This detonation wave provides the necessary high muzzle pressure-temperature energy release, which creates the required acoustical/visual signatures. Two necessary conditions must be satisfied to support the development of a detonative wave. First, the mixture ratio of fuel and oxidizer near the spark plug must be within flammability limits to initate and propagate the deflagration flame front. Second, for the deflagration flame front to rapidly transition to a detonation wave the fuel/oxidizer mixture ratio in the confined volume of combustion chamber must be within the detonation limits.
A related problem in prior art weapons effects simulating combustion chambers has been in the tendency for the combustion flame to flash back through the fuel injectors, nozzles and manifolds, disrupting operation and creating a safety hazard.
Also prior art weapons effects simulators have not been able to accurately produce the sound level, fundamental frequencies, overtones and muzzle flash made by actual guns. A skilled observer can acoustically distinguish types of real weapons from a considerable distance, and it is a vital training element to learn to identify the lethality of weapons types before entering into engagement in combat. It would be disastrous to a trainee to learn and become familiar with weapons signatures during training that were different in terms of distance, range, caliber and lethality than the real weapons to be encountered in combat.
Presently known weapons effects simulators also have been physically larger than the real weapons, making the firing of such simulators unrealistic for trainee shooters. This has greatly diminished the value of training by failure to provide a realistic surrogate weapon that can develop familiarity and skill that is transferable from the surrogate to the actual combat weapon. Not only are prior art simulators oversized, but a number of them have been unable to operate at low temperatures; as they have employed fuels, such as propane or butane, that will not boil to provide adequate gas pressure at the subfreezing temperatures that are considered normal for weapons operation.